Equilibrium (harbor process), alloys, LCAs, water Questions and Answers 2023

Equilibrium (harbor process), alloys, LCAs, water Questions and Answers 2023 Why do we need fertilisers -plants need nitrogen to grow + make proteins When the crop is harvested, most parts don't rot back into the soil -> less nutrients for next plant -nitrogen is insoluble in water and plants need to absorb a soluble form of nitrogen -nitrogen from the air -> nitrogen compounds mean they can be absorbed What is equillibrium? the rate of the forward reaction is equal to the rate of the reverse reaction What is the effect of changing conditions on Equilibrium -system is no longer at equilibrium -concentrations of all substances will change until equilibrium is reached again -If conc of reactant is increased, more products will be formed until e is reached again -if conc of product decreases, more reactants will react until e is reached again How does pressure affect equilibrium? Increase in pressure, e position shifts towards the side with smaller no. molecules decrease in pressure, e position shifts towards side w larger no. molecules How does temp affect equilibrium -temp of a system increased: -relative amount of products increases for an endothermic reaction -relative amount of products decreases for exothermic reaction Temp of system decreased -relative amount of products at equilibrium decreases for endothermic -relative amount of products at e increases for exothermic Ammonia raw materials Nitrogen from the air Hydrogen from natural gas which contains methane (CH4). Methane + steam -> hygrogen and carbon monoxide What is the Haber process? -method of manufacturing ammonia -where reaction reaches dynamic equilibrium How to make ammonia + equation -purify nitrogen and hydrogen (react in oxygen vessel) -passed over iron catalyst at high temp (450) and high pressure (200atm) -ammonia is removed by cooling the gas so it liquifies (increases yield) -> then separated from nitrogen and hydrogen gas -unreacted nitrigen + hydrogen recylced back into reaction mixture -> re-compressed and reheated...return to reaction vessel Describe haber process diagram Why is nitric acid added to ammonia? Forms ammonium nitrate salt which can be used as fertiliser Ammonia equation N2 + 3H2 <=> 2NH3 How does pressure affect the habor process? What about temp? -increase of pressure shifts equillibrium position to the right bc less molecules -> more ammonia produced in order to reduce pressure -200atm used to avoid higher costs of building a stronger chemical plant (compromise). -lower yield than higher pressures but reasonable ROR What state does pressure affect Only gases grrr Which way is endothermic/exothermic in habor reaction? What is the effect of temp? Forward reaction is exothermic -lowering temp would increase the amount of ammonia in the reaction mixture -raises temp + opposes change induced -ROR would be too slow (bc...) + effect of catalyst reduced at low temp -ammonia is made commercially so needs to be fast! -> compromise temp of 300 degrees :) (even tho yield reduced) What is the effect of a catalyst on habeor process -speeds up ror of both forward and reverse reactions by same amount -does not affect yield -but causes ammonia to be produced more quickly (important for economics) What is Le Chatelier's principle? When a reaction at equilibrium is changed, it will seek to counteract that change changes include: pressure, temp, concentration -> used to predict what happens so that a new equillibrium position is reached How else can we reduce costs (habor process) -nitrogen + hydrogen recycled (cost of making reactants from raw materials reduced) -Heat from exothermic reactions used to generate steam, turbine, electricity generator what can ammonia be used for? manufacture ammonium salts and nitric acid What are NPK fertilisers? Fertilisers containing compounds of: nitrogen, phosphorous, potassium -they are formulations of salts Where does potassium come from? Which things can be extracted and used as fertilisers directly after mining? what can't Potassium salts eg potassium chloride and potassium sulphate Phosphate rock can't: must be chemically processed What is phosphate rock treated with? nitric acid, sulfuric acid, phosphoric acid Formula for phosphate PO₄³⁻ How is phosphate rock treated and why ? -cannot be used directly on soil as it is insoluble in water -rock treated with acids to make fertiliser salts Nitric acid: -produces phosphoric acid H3PO4 and calcium nitrate Ca (NO3)2 ! Phosphoric acid cannot be added directly to plants ->neutralised with ammonia to produce ammonium phosphate (NH4)3PO4 Sulfuric acid: -single superphosphate: mixture of calcium phosphate + calcium sulphate Phosphoric acid: Triple superphosphate Both produce soluble salts that can be used as NPK fertiliser What is the main compound in NPK fertilisers? ammonium nitrate (NH4NO3) -we use ammonia from harbour process Why is ammonia important in making fertilisers -alkali and when involved in neutralisation reactions it produces nh4+ ion -can also be oxidised to make nitric acid (HNO3) (provides nitrate) Ammonium hydroxide and... Ammonium hydroxide + nitric acid → ammonium nitrate + water NH4OH + HNO3 → NH4NO3 + H2O what type of reaction is ammonia and nitric acid neutralisation